The present invention relates to methods of inhibiting retroviral integrases with dicationic bis-benzimidazoles.
The genome of the typical retrovirus encodes three primary enzymes that mediate the virus replication cycle. Reverse transcriptase converts the viral RNA genome into a double stranded DNA. Integrase nonspecifically inserts this DNA copy into the host cell genome, and protease cleaves viral structural and nonstructural proteins into their mature forms.
An essential step of the retroviral life cycle is the integration of its double-stranded DNA copy into the host genome. H. Sakai et al, J. Virol. 67, 1169-74 (1993). This process requires highly conserved sequence recognition and cleaving steps. For this reason, a therapeutic agent that can interrupt this process should be an effective and specific antiviral agent. A protein at the C-terminus of the viral polymerase, integrase (IN), is the only viral protein required for this process. R. LaFemina et al., J. Virol. 66, 7414-7419 (1992).
A. Fesen et al., Proc. Natl. Acad. Sci. USA 90, 2399-2403 (1993) discuss investigations using an in vitro integrase assay of a variety of chemicals as potential human immunodeficiency virus type I (HIV-1) integrase inhibitors. The article reports several topoisomerase inhibitors, such as doxorubicin, mitoxantrose, ellipticines and quercetin as potent inhibitors. While some topoisomerase inhibitors were excellent anti-integrase agents, no correlation was observed with antiviral effects. This is believed to be at least partially due to the fact that a number of topoisomerase inhibitors have severe cytotoxic effects, depending upon their mechansim of inhibition.
R. LaFemina et al., J. Virology 56, 7414-7419 (1992) reports studies assessing the usefulness of the integrase enzyme as a target for specific HIV-1 anti-viral therapeutic agents by determining its absolute requirement for productive HIV-1 infection. The article reports the results of the introduction of specific amino acid substitution into recombinant integrase and assesses the ability of the mutant proteins to properly mediate specific and non-specific cleavage as well as integration.
A first aspect of the present invention is a method of inhibiting retroviral integrase (e.g. in vitro, or in a subject in need of such treatment). The method comprises administering to the subject or contacting to the retroviral integrase an effective retroviral integrase-inhibiting amount of a compound according to Formula (I): 
wherein:
R1 and R2 are each independently selected from the group consisting of H or lower alkyl, or R1 and R2 together represent xe2x80x94(CH2)mxe2x80x94 wherein m is from two to four;
R3 is H or lower alkyl; and
X is C1 to C2 saturated or unsaturated alkyl containing up to one double bond (e.g., xe2x80x94(CH2)n wherein n is from 1-2, which is unsubstituted or substituted from 1 to 2 times with lower alkyl, and which is saturated or unsaturated and contains up to one double bond);
or a pharmaceutically acceptable salt thereof.
In a preferred embodiment of the invention, R1 and R3 are each H; R2 is H or lower alkyl; and x is selected from the group consisting of xe2x80x94CH2xe2x80x94CH2xe2x80x94 and xe2x80x94CHxe2x95x90CHxe2x80x94 and any of the foregoing substituted from 1 to 2 times with lower alkyl; and the pharmaceutically acceptable salts thereof. Currently preferred compounds are bis[5-amidino-2-benzimidazolyl]methane; 1,2-bis[5-amidino-2-benzimidazolyl]ethane; 1,2-bis[5-amidino-2-benzimidazolyl]ethene; 1,2-bis[5-isopropylamidino-2-benzimidazolyl]ethene, or pharmaceutically acceptable salts thereof.
A second aspect of the present invention is a method of combatting a retroviral infection (e.g. in vitro, or in a subject in need of such treatment). The method comprises administering to the subject or contacting to the retrovirus an effective retroviral infection combatting amount of a compound according to Formula (I) as given above or a pharmaceutically acceptable salt thereof. Currently preferred compounds are bis[5-amidino-2-benzimidazolyl]methane; 1,2-bis[5-amidino-2-benzimidazolyl]ethane; 1,2-bis[5-amidino-2-benzimidazolyl]ethene; 1,2-bis[5-isopropylamidino-2-benzimidazolyl]ethene, or pharmaceutically acceptable salts thereof.
Compounds of formula I, or there pharmaceutically acceptable salts, may be included in a therapeutically effective amount in a pharmaceutically acceptable carrier to provide pharmaceutical formulations, with the therapeutically effective amount being effective to carry out the methods set forth above.
Further aspects of the present invention include the use of compounds of Formula (I) above and their pharmaceutically acceptable salts for the preparation of a medicament for inhibiting retroviral integrase, or for combatting a retroviral infection.
The foregoing and other objects and aspects of the present invention are explained in detail in the specification set forth hereinbelow.